Yes, there is inappropriate language. There is also mention of sex. Scott Westerfeld wrote a vampire story that made sense. Instead of vampires being undead gothic people that bite others for fun, vampires are people who have been infected with a parasite that makes them into a vampire-like individual, a.k.a. a "peep." It would be dumb if the parasite spread by having one person cough on another. Scott Westerfeld did his research and based his story off of theories and facts about existing parasites. It makes sense for the parasite to want to spread itself and it makes sense for it to be transmitted sexually. Scott Westerfeld is not trying to be distasteful, he is being realistic. If you want your teenager to read about a world where everything is peachy, no one swears, and everyone is loving and kind then do that. I can't control how you raise your kid. My point is, this book is modeled after reality (except the vampire and evil worm part, of course), and in reality, tons of people swear and smoke and have sex. The book does not make a point to encourage pre-marital sex or smoking, therefore, it is not as harmful as a previous reviewer seemed to feel. I suggest this book for a mature 12 or 13 year old. If you shelter your teenager and they still believe in unicorns and gold at the ends of rainbows and you want to continue your poor treatment of them, then do not have them read this. YOU should know your kid best. Just be aware that it does discuss parasites. The book didn't make me queasy, but I'm not so much the queasy type. Also know, that while parasites are generally a topic that makes you're average Joe disinterested or bored, Scott Westerfeld makes them quite intriguing. I know that I loved this book. It is very worth reading. It is educational. It teaches people about parasites and their functions. It extrapolates from these facts and creates a believable (if you're good at suspending disbelief for the sake of a good movie or read) story... or at least more believable story than the "girl-falls-in-love-with-sexy-vampire" story. This book is enjoyable and truly, honestly unique, interesting, and amazing. I think you're depriving your kid if they're 13 and older and you won't let them read books like this. I hope that my review helped and happy reading!